Author(s): Chaolin Wang; Shengtao Du; Guoxiang Wu
Linked Author(s):
Keywords: Local scour; Pile groups; Silty sand; Steady currents; Experimental investigation
Abstract: Pile foundations are widely used in offshore and coastal engineering and therefore pile groups can be found in marine platforms, solar photovoltaic clustered piles, bridges and other offshore structures. The deployment of pile groups will perturb the dynamical environment in their immediate vicinity and has the potential to increase local sediment transport, which in turn causes local scour of the sand bed and finally reduces pile-carrying capacity. Meanwhile, with the human exploitation of silty coasts and seabed, the problem of local scour in silty sand needs to be studied urgently. For example, Figure 1 illustrates the problem of current-induced local scour around solar photovoltaic cluster piles in the region of silty coastal zones, which has been of great concern in this regard. However, current research on current-induced local scour around pile groups focused on non-cohesive sand beds or local scour around a single pile in a silty sand bed, with a lack of studies on current-induced local scour around pile groups under silty sand beds. In this present study, a series of experimental local scour tests around pile groups with different pile arrangements under steady currents were conducted to analyze the effect of pile spacing (G/D) and number of rows (Nr) on scour around group piles in silty sand beds. Sand bed topography evolutions and temporal scour depth in the pile groups vicinity under different tests were studied comprehensively. Meanwhile, the equilibrium scour depths around pile groups were also compared to those around a single pile to investigate the influence of pile groups interactions on scour. The results indicated that the pile spacing (G/D) and number of rows (Nr) had a significant effect on the scour topography and depth. Decreasing pile spacing (G/D) led to an increase in scour depth, while also reducing the extent of the scour pit. Additionally, the interference between pile groups amplified the scour depth of rear piles, especially with a higher number of rows. Furthermore, the development of local scour topography in cohesive sand beds differed from that in generally non-cohesive sand beds due to the cohesive forces between the silty sand particles. Scour pits have the potential to ultimately experience collapse, thereby leading to a reduction in the maximum scour depth surrounding the pile and an exacerbation of the scope of scour phenomenon.
Year: 2024